Oscillator system



July 23, 1935.

J. B. DOW

OSCILLATOR SYSTEM Filed July 1, 1932 INVENTOR tlnni nys B. D0 w.

ATTORNEY Patented July 23, 1935 OSCILLATOR SYSTEM 7 Jennings B. Dow-,'Washington, LC assignor to 7 Radio Corporationof America, a corporationof Delaware Application July '1, :19s2 ;seria1-No. accuse f9 cl ims.(erase -self.

(Granted under "the" act of March 3, 1883, as

' amended April 3'0, 1928; 370 0. G. 757).; V

invention relates broadly to oscillatorsystemsand more particularly to;a'balanced o'scil-' latorsy'ste'm.

.....On'e-of the objects of my invention is to provide. a balancedbridge type of oscillation generator; A ,3 Another object of myinvention'is to provide abalancedoscillatorin which the frequency ofoscillation is relatively: free from the influence of external circuitswhich may be coupled to the system. r I vA still further object of myinvention is toiprov-ide'a balanced bridge type of oscillation generator, the output portion of which forms noessential part of theoscillation generating means. Other: and further objects of my inventionwill be understood from thespecificationhereinductance, capacity andresistance are in part,

transferred in the form of eguivalences into the oscillation generator.This transfer 'of equivalencesresults in changing, those electricalconstantsi'of the system which determine the frequency of oscillationand thus'makes the frequency o'f'oscillation' a function of the load. A

present invention -covers a method of arranging the oscillationgenerator and its output work circuit in a balanced or bridge arrangement so thatthe'efiect of variable load conditions wilt-be reduced.

- I 'In' th'e circuit of- Fig. 1, reference character lin- 'di'cates anelectron tube having" a cathode 2, a contro1 grid-3',an inner anode 4and an outer anode 5} The tube maybe ofthe conventional dour-clementtype or it may be of a type especially designedfor this kind of service.The cathode 2 is heatedby battery' 8-and isconnected to the'rotor of aconventional split Variable con- -denser: 'l-.--Obvious1y two or morecondensers in series with the center connection maderto the cathodemight Just as" well be employed. 2 The are sectionsof the'fcondenser 'lare connected to the opposite ends of .an inductance-and together iormresonant circuit 9. One end oflthe resonant circuit 9 is connected"through a blocking condenser IO vtocontrol grid 3. 'A grid leak llconnectsthe control gridand cathode for biasing the former at thedesired potential; The opposite end of resonant circuit 9 connects toinner anode A which is supplied at the proper positive potentialwithwrespect to cathode 2 b'ylits i connection to anode battery. .l2through chokeicoil l3.

The circuit thus farjdescribed is theiamiliar Colpitts oscillator. and"with such a circuit, .it is conventional practicertoi connect or couplethe load to resonant circuit 9.- In the particular fcrmof my invention:shown in Fig. 1,,I do; not do this in the'conventional manner butinstead, I

derive energy from. the. oscillator through the medium of an outputcircuit connected between outer anode'5 and a point along inductance 8.The outer anode 5 is .maintainediat the desired potential withrespecttocathode 2 by its connece tion to anode battery .52 throughchoke coil i l. The output circuit comprises blocking condenser l5 andresonant circuit, H5 in series connection between outer ancdeft and'ta'pconnection ll :alonginductance '8. Resonant circuit. It consists ofinducta'nceul'S an'dvariable capacity IS in parallel; :Reson'antcircuit. l6 may be tuned to the samesfrequency as resonantcir'cuit 9.01"it may be tuned to al harmonically related one.

7 Resonant circuit lfi' may bereplaced by any other: form of impedancesuch as an inductance or aresista'nce; Choke coils;rl3 and I4 mayalso:be-repla'ced byothenhigh impedancesl such as resistances.The'1remainder-0f the circuit of Fig. comprises:balancing condenser 20connected-betwe'encontrolgrid 3 and outer anode 5. The 'functionofbalancing" condenser 20 will be madeicle'ar in what follows. i

Fig. z shows in simplified formthe equivalent high.frequency portion'ofthe circuit of Fig. 1. .All partsof Fig. 1- whichiare not essential'toan understanding of the 'principles of my invention are omitted from the:circuit of Fig. 2. In the circuit oi Fig. 2-:the cathode .2, controlgrid 3, inner anode Land'outer. anode 5. are indicated attlie apexes ofthe bridge. Reference character vCa.idenotesithatportion-of condenser lof Fig.

1.which isbe'tween control grid 3 andcathode 2. The grid to cathodeintereleme'nt capacity is'con-- z'si'deredxlumpe'dwithithat ofcapacity'cv'a. Reference character Cisdenotes that portionof con.-denser jl of Fig; lwhich is betweencathode 2 and inner anode 4.4Theinterelement capacity between cathode and inneranode. is consideredlumped with, capacity Cit. Inductance 8 isbetween .control-grid 3- -andginner anode 4 as in Fig.

the interelement capacity between inner anode 4 and outer anode 5whereas C20 denotes the capacity of balancing condenser 20 of Fig. lwhich is connected between control grid 3 and outer anode 5. Resonantcircuit l6 which comprises the high frequency portion of the outputcircuit is connected between outer anode 5 and a point along inductance8. Now, C; is fixed by the design of tube employed, and the ratioCva/Cn, may be fixed by the design of condenser 1. Therefore if- C20 isso chosen that,

V zo C71? V- then, neglecting electron flow, an alternating potentialacross inductanceB will not produce a potential between cathode 2 andouter anode 5 nor will an alternating potential be produced acrossresonant circuitlO if tap ll on inductance 3 is so placed that itsuitably divides the impedance of'inductance. 8. This is equivalent tostating that the generated oscillations, neglecting electron flow, arenot coupledtothe output circuit l6 through the interelement capacitiesof the tube.

From Equation (1) it may be deduced that any suitable impedances Z maybe employed in place of the capacities C. Using the same subscripts asindicated in Equation (1) it will then be seen that the followinggeneric equation is to be satisficd by the conditions under which thesystem my invention may be operated:

Further consideration will show that the oscillation generating portionof the circuit acts so as to satisfy the conditions required foroscillation, for determining the frequency and for causing pulses ofelectrons tobe projected through the grid-like structure of inner anode4 to the outer anode 5. The pulses of electrons impinging upon outeranode 5 cause correspondingva'riations-in potential across choke coil.l4 and coin.- cidentally,.across resonant. circuit Hi to which thedesired load may. be coupled.

As previously stated, the oscillation generating portion of thecircuitof Fig. 1 is of the Colpitts type. Obviously. any other form ofoscillator might have been employed with equal facility, for example,had the Hartley type been chosen Equation (2) would still hold; The onlydifference in that case would be that branches C78 and 07b of Fig. 2would be inductive whereas inductance 8 would be replaced by a capacitybranch.

My invention comprises meansxfor balancing out the effect ofinterelement impedance which may exist betweenan auxiliary element andthose elements of an oscillation generator which may be positionedwithin the same electron tube. It will be noted that Equations (1) and(2) are inde pendent 'of any steady potentials which may exist or beimpressed in the circuit. It is also apparent from the equations thatthey are independent of the frequency and amplitude of the existingalternating potentials.

Ihave found the oscillator circuit of my invention highly stable in itsoperation and while I have described it in certain of its preferredembodiments I desire it to be understood that modifications may be madeand that no limitations are intended other than are imposed by the scopeof the appended claims.

The invention described herein may be manufacturedand used by or for theGovernment of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

' What I claim asnew and desire to secure by Letters Patent of theUnited States is as follows: -1. An oscillation generator comprising anelectron tube having a cathode element, a control grid element, and agrid-like anode element, and branch circuits connecting said elements,in combinationwith a second anode element within said tube and a branchcircuit interconnecting said second anode element with said controlgrid, the

characteristics of said combination being such that the impedance of thebranch between said control grid element and said second anode elementis substantially equal to the product. of the interelement impedancebetween said'grid-like anodeelement and said second anodes element, andthat of the; branch circuit between said cathode element and saidcontrol grid'element divided by the impedance of the branch circuitbetween said cathode element and said grid-like anode element, andinaddition to said combination an output circuit connecting said secondanode element with a point along the branch circuit between said controlgrid element and said grid like anode element.

, 2. An electron tube having a cathode, a con trol grid and a grid-likeanode, circuits interconnecting said electrodes wherewith an oscillationgenerator is provided, a second anode within said tube having a reactiveconnection with said con trol grid, and ,an output circuit disposedbetween said second anode and a point along that one of said oscillationgenerator circuits which inter-.- connects the control grid and thegrid-like anode, the arrangement being such that the alternatingpotential produced upon said. second "anode through the interelementcapacity existent be.-

tween said anodes is substantially equal to and opposite in phase tothat induced upon said second anode through said reactive connection.

the frequency generated, means including a resonant circuit foroperatively associating said in-.-

put and output circuits with oneanother so. as'to produce oscillations,a resonant ;circuit interconnecting said fourth electrode and a pointalong the aforesaid resonant circuit, and means whereby the effect ofinterelement capacities in producing high frequency potentials ,uponsaid fourth electrode is substantially neutralized.

4. An oscillationgeneratorincluding an ,electron tuberhaving a cathodeelement, acontrolgrid element and a: grid like anode element, and branchcircuits connecting said elements, in com.- bination with. an auxiliaryelement within said tube and a branch circuit interconnecting saidauxiliary element with said control? grid, the characteristics of-v saidcombination-being :such

that the impedance of the branch between said control grid element andsaid auxiliary element is substantially equal to the product of theinterelement impedance between said grid-like anode element and saidauxiliary element, and that of the branch circuit between said cathodeelement and said. control grid element, divided by the impedance of thebranch circuit between said cathode element and said grid-like anodeelement, and in addition to said combination, a resonant circuitdisposed in series connection between said auxiliary element and a pointalong the branch circuit between said control grid element and saidgrid-like anode element.

5. An electron tube having a cathode, a control grid and grid-likeanode, circuits interconnecting said electrodes wherein an oscillationgenerator is provided, an auxiliary electrode within said tube having areactive connection with said control grid, and a work circuit disposedbetween said auxiliary electrode and a point along that one of saidoscillation generator circuits which interconnects the control grid andthe grid-like anode, the arrangement being such that the alternatingpotential produced upon said auxiliary electrode through theinterelement capacity existent between said grid-like anode and saidauxiliary electrode is substantially equal to and opposite in phase tothat induced upon said auxiliary electrode through said reactiveconnection.

6. In a device for generating oscillations, an

electron tube at least three electrodes of which in combination withinput and output circuits therefor are adapted to generate oscillations,an auxiliary electrode within said tube, means including a resonantcircuit for operatively associating said input and output circuits withone another so as to produce oscillations, a-second resonant circuitdisposed between saidauxiliary electrode and a point along the aforesaidresonant circuit, and means whereby the effect of interelementcapacities in producing high frequency potentials upon auxiliaryelectrode is substantially neutralized.

'7. In a device for generating oscillations, an electron tube at leastthree electrodes of which in combination with interconnecting circuitstherefor are adapted to generate oscillations, an auxiliary electrodewithin said tube and an additional circuit connecting said auxiliaryelectrode with a point along one of said first mentioned circuits, andmeans whereby the effect of interelement capacities in producing highfrequency potentials upon said auxiliary electrode is substantiallyneutralized.

8. A device for generating oscillations in accordance with claim '7wherein said additional

